Moon orbit formation navigation microsatellite inter-satellite measurement system and method

Abstract

The invention provides a moon orbit formation navigation microsatellite inter-satellite measurement system and method, and relates to the technical field of deep space exploration, the system comprises a master satellite and a slave satellite, and a Ka inter-satellite link is established between the master satellite and the slave satellite; the master satellite and the slave satellite both send timing inter-satellite measurement signals, receive timing inter-satellite measurement signals from the opposite side, measure the time difference between a local timing signal and the received timing signal of the opposite side to obtain the pseudo-range of the satellite, and the two satellites exchange the pseudo-range through an inter-satellite link to solve the inter-satellite distance and the time difference. Accurate time synchronization of two satellites is not needed, a measurement result can be directly obtained on the satellites, ground calculation is not needed, and ground resources are saved; the satellite platform and the antenna design of the slave satellite are simplified, and the weight and the cost of the satellite are reduced.

Description

Technical Field

[0001] The present invention relates to the field of deep space exploration technology, and in particular to a lunar orbit formation navigation microsatellite intersatellite measurement system and method. Background Art

[0002] In recent years, the global deep space exploration has achieved vigorous development. All major space powers have proposed deep space exploration missions such as lunar exploration, planetary exploration, and planetary defense, and are gradually implementing them. With the continued exploration of the lunar poles, the far side of the moon and other areas that are invisible to the earth, as well as the exploration of more distant planets and even the solar system, the existing navigation system cannot meet the actual engineering needs. Deploying a navigation satellite network around the moon and building a lunar navigation system as the infrastructure of the cis-moon space can expand the coverage of reliable satellite navigation and provide support for lunar and even deep space exploration missions.

[0003] If the accuracy of the navigation satellite's own orbit determination is low, it will not be able to provide users with high-precision positioning and navigation services. In order to realize and enhance the autonomous orbit determination and autonomous navigation functions of navigation satellites, existing navigation satellite constellations are all equipped with inter-satellite links and inter-satellite measurement functions to serve autonomous orbit determination and satellite-ground joint orbit determination, thereby improving the orbit prediction accuracy of navigation satellites and further realizing the long-term maintenance of satellite navigation and positioning performance without the support of ground stations.

[0004] Compared with large spacecraft, microsatellites are small, light, easy to form a formation and network, and are gradually gaining attention in the field of deep space exploration. However, the hardware and software resources of microsatellites are relatively limited, so the intersatellite measurement of microsatellites needs to meet the measurement accuracy while having the characteristics of low hardware complexity and simple calculation processing.

[0005] The Chinese invention patent with publication number CN117318786A proposes a method for measuring intersatellite links in the Earth-Moon space with extremely large delays based on the Beidou navigation system. The distance of the intersatellite link is calculated based on the one-way ranging values ​​calculated by the Beidou navigation satellite and the Earth-Moon spacecraft. This patent requires the use of Beidou satellite signals. Satellites in lunar orbit are far away from the Earth, so it is difficult to use Beidou satellite signals.

[0006] The Chinese invention patent with publication number CN109283557A proposes a two-way pseudo-code assisted carrier high-precision inter-satellite ranging system and method, which uses two-way pseudo-code regeneration or forwarding technology to assist carrier coherent forwarding to obtain the absolute distance between the master and slave satellites. The slave satellite in this patent needs to coherently forward the carrier signal of the master satellite and regenerate or forward the pseudo-code ranging signal of the master satellite. The hardware and algorithm are relatively complex, and time synchronization between the master and slave satellites cannot be achieved.

[0007] The Chinese invention patent with publication number CN110708754A proposes a power allocation method for integrated ranging and communication signals between navigation satellite constellations, which calculates the intersatellite link characteristics based on the relative distance between navigation satellites, thereby adjusting the power ratio of communication signals and ranging signals. This patent does not involve the implementation of the intersatellite measurement system.

[0008] The Chinese invention patent with publication number CN113959431A proposes a high-precision inter-satellite distance and time difference joint measurement method, which calculates the distance and time difference between satellites based on a multi-satellite measurement scheme based on a time division system and the ADS TWR method. The invention mainly proposes the measurement principle and does not involve the on-board design and implementation of the inter-satellite measurement system. Summary of the invention

[0009] In view of the defects in the prior art, the present invention provides a microsatellite inter-satellite measurement system and method for lunar orbit formation navigation.

[0010] According to a lunar orbit formation navigation microsatellite intersatellite measurement system and method provided by the present invention, the scheme is as follows:

[0011] In a first aspect, a lunar orbit formation navigation microsatellite intersatellite measurement system is provided, the system comprising: a master satellite and a slave satellite, a Ka intersatellite link is established between the master satellite and the slave satellite;

[0012] The master satellite and the slave satellite both send timing inter-satellite measurement signals and receive timing inter-satellite measurement signals from each other, measure the time difference between the local timing signal and the received timing signal of the other party to obtain the local satellite pseudo-range, and the two satellites exchange pseudo-ranges through an inter-satellite link, that is, solve the inter-satellite distance and time difference.

[0013] Preferably, the master satellite comprises: a high-gain Ka directional antenna, a master satellite ranging payload and a master satellite platform; the slave satellite comprises: a low-gain Ka wide-beam antenna, a slave satellite ranging payload and a slave satellite platform;

[0014] The high-gain Ka directional antenna and the low-gain Ka wide-beam antenna complete the transmission and reception of intersatellite measurement signals;

[0015] The master satellite ranging payload and the slave satellite ranging payload measure the inter-satellite distance and time difference;

[0016] The master satellite platform provides power, pulse-per-second signals, time broadcast and control instructions for the ranging payload, receives intersatellite measurement results and analog telemetry of the ranging payload, provides attitude adjustment and control for intersatellite measurement, and transmits the measurement results to the ground;

[0017] The slave satellite platform provides power and control instructions for the ranging payload, receives the inter-satellite measurement results and analog telemetry of the ranging payload, provides attitude adjustment and control for the inter-satellite measurement, and transmits the measurement results to the ground.

[0018] Preferably, the master satellite adopts a high-gain Ka directional antenna. During inter-satellite measurement, the master satellite needs to adjust its attitude to align the antenna beam with the slave satellite.

[0019] The slave satellite adopts a low-gain Ka wide-beam antenna. During inter-satellite measurement, the slave satellite points the low-gain Ka wide-beam antenna in the direction of its velocity or in the opposite direction according to its relative position relationship with the master satellite.

[0020] Preferably, if the inter-satellite measurement signal cannot be locked, the master satellite platform adjusts the satellite attitude and uses a spiral scanning method to adjust the beam pointing of the high-gain Ka directional antenna.

[0021] Preferably, the master satellite is the initiator of the inter-satellite measurement, and the slave satellite is synchronized to the master satellite at the time of signal transmission;

[0022] The master satellite platform sends a pulse-per-second signal to the ranging payload. After the master satellite ranging payload receives the pulse-per-second signal and determines it is valid, it starts sending intersatellite measurement signals at the falling edge of the pulse-per-second signal. After the slave satellite ranging payload receives the signal and successfully demodulates it, it starts sending intersatellite measurement signals. After the master satellite ranging payload receives the slave satellite signal and successfully demodulates it, both parties start measuring using the two-way time comparison method. The slave satellite ranging payload corrects the sending time of the slave satellite signal based on the measurement results and sends it to the master satellite for time synchronization.

[0023] Preferably, the master satellite ranging payload and the slave satellite ranging payload both include: a Ka channel module and a digital baseband module;

[0024] The Ka channel module includes: a transmitting channel and a receiving channel, which support simultaneous transmission and reception. The transmitting channel up-converts, filters, and amplifies the central signal output by the digital baseband module and sends it to the antenna. The receiving channel amplifies, filters, and down-converts the radio frequency signal from the antenna into an intermediate frequency signal and outputs it to the digital baseband module. Both up-conversion and down-conversion adopt a single frequency conversion scheme.

[0025] The digital baseband module implements baseband signal processing and ranging algorithms, modulates the spread spectrum code sequence of inter-satellite measurement, digitally up-converts the frequency to generate an intermediate frequency signal, and outputs the signal to the Ka channel module; receives the intermediate frequency signal of the Ka channel module, performs pseudo code despreading, pseudo code synchronization, carrier synchronization and frame synchronization after digital down-conversion, obtains the local satellite time difference measurement value required by the two-way time comparison method by using pseudo code correlation operation, analyzes the inter-satellite measurement frame to obtain the time measurement value of the other satellite; and calculates the inter-satellite distance and time difference.

[0026] Preferably, the digital baseband module comprises: an intermediate frequency transceiver circuit, a digital signal processing circuit and a clock generation circuit;

[0027] The intermediate frequency transceiver circuit uses an integrated transceiver chip to realize the conversion between baseband data and intermediate frequency signals, meeting the requirements of miniaturization, low power consumption and flexibility;

[0028] The digital signal processing circuit uses an FPGA chip to complete baseband data processing, and is configured with an anti-fuse to refresh the FPGA chip and a watchdog reset circuit to improve the product's single-particle resistance;

[0029] The clock generation circuit cascades a chip-level atomic clock and a tamed constant temperature crystal oscillator to provide a reference clock and a reference frequency for a digital baseband module and a Ka channel module.

[0030] Preferably, the inter-satellite measurement signal is a Ka-band radio frequency signal of a modulated pseudo code signal and an inter-satellite measurement frame;

[0031] The pseudo code signal is used to measure the time difference between the local timing signal and the received timing signal of the other party;

[0032] The inter-satellite measurement frame includes the time difference measurement result of the local satellite and the measurement timestamp. The master satellite and the slave satellite exchange the measurement results through the inter-satellite measurement frame, thereby completing the settlement of the inter-satellite distance and time difference on the local satellite.

[0033] In a second aspect, a method for inter-satellite measurement of a lunar orbit formation navigation microsatellite is provided, the method comprising:

[0034] Step 1: The ground selects the intersatellite measurement arc according to the orbit prediction and sends instructions to the satellite;

[0035] Step 2: The master satellite platform and the slave satellite platform adjust their attitudes;

[0036] Step 3: The ranging payloads of the master and slave satellites are turned on for a set threshold time;

[0037] Step 4: The master satellite and the slave satellite establish an inter-satellite link, and the inter-satellite measurement signal is locked;

[0038] Step 5: The slave satellite sends synchronization signals to the master satellite;

[0039] Step 6: Obtain intersatellite measurement results;

[0040] Step 7: After the intersatellite measurement is completed, the master satellite and the slave satellite turn off the master satellite ranging payload and the slave satellite ranging payload, and the master satellite and the slave satellite adjust their attitude to the normal flight attitude towards the sun.

[0041] Preferably, step 4 comprises:

[0042] The master satellite platform sends time broadcast and second pulse signals to the ranging payload, and the master satellite ranging payload starts to send timed inter-satellite measurement signals to the slave satellite at the falling edge of the second pulse;

[0043] If the slave satellite cannot lock onto the master satellite signal, the master satellite platform adjusts the satellite attitude and uses spiral scanning to adjust the beam pointing of the high-gain Ka directional antenna;

[0044] After the slave satellite receives the master satellite signal and successfully demodulates it, it sends a timed inter-satellite measurement signal to the master satellite; the master satellite ranging payload receives the slave satellite signal and successfully demodulates it.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. The present invention adopts a two-way comparison method to obtain the distance and time difference between satellites. The two satellites do not need precise time synchronization. The measurement results can be obtained directly on the satellite without ground calculation, thus saving ground resources.

[0047] 2. The present invention simplifies the antenna design of the slave satellite, reduces the requirements for the attitude pointing accuracy and stability of the slave satellite, and is conducive to reducing the weight and cost of the entire slave satellite;

[0048] 3. The present invention adopts a combination of a high-gain Ka directional antenna and a low-gain Ka wide-beam antenna, which takes into account both improving the inter-satellite measurement distance and reducing the difficulty of inter-satellite beam alignment;

[0049] 4. The ranging payloads of the master satellite and the slave satellite of the present invention have the same hardware design except that the transmitting and receiving frequencies are interchanged, which is conducive to the batch design of the payload and reduces the difficulty and cost of debugging;

[0050] 5. The ranging payload of the present invention adopts a chip-level atomic clock and a disciplined constant temperature crystal oscillator cascade to provide a reference clock, which combines the high accuracy of the chip-level atomic clock and the low phase noise performance of the constant temperature crystal oscillator, and is conducive to improving the accuracy of intersatellite measurement.

[0051] Other beneficial effects of the present invention will be explained in the specific implementation manner through the introduction of specific technical features and technical solutions. Through the introduction of these technical features and technical solutions, those skilled in the art should be able to understand the beneficial technical effects brought about by the technical features and technical solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0053] Figure 1 It is a schematic diagram of the intersatellite measurement system of the present invention;

[0054] Figure 2 This is a flow chart of the intersatellite measurement of the present invention. DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0056] The embodiment of the present invention provides a lunar orbit formation navigation microsatellite intersatellite measurement system, which realizes intersatellite measurement within a range of 400km between the master satellite and the slave satellite. Figure 1 As shown, it includes: a master satellite and a slave satellite, and a Ka inter-satellite link is established between the master satellite and the slave satellite;

[0057] Both the master satellite and the slave satellite send timing inter-satellite measurement signals and receive timing inter-satellite measurement signals from each other. The time difference between the local timing signal and the received timing signal of the other party is measured to obtain the pseudo-range of the local satellite. The two satellites exchange pseudo-ranges through the inter-satellite link, that is, the inter-satellite distance and time difference are solved.

[0058] The master satellite includes: high-gain Ka directional antenna, master satellite ranging payload and master satellite platform; the slave satellite includes: low-gain Ka wide-beam antenna, slave satellite ranging payload and slave satellite platform; the master satellite ranging payload and the slave satellite ranging payload have the same hardware design except that the transmitting and receiving frequencies are interchanged; the master satellite ranging payload and the slave satellite ranging payload both include Ka channel module and digital baseband module. The Ka channel module includes transmitting channel and receiving channel, and the digital baseband module includes intermediate frequency transceiver circuit, digital signal processing circuit and clock generation circuit.

[0059] The high-gain Ka directional antenna and the low-gain Ka wide-beam antenna complete the transmission and reception of intersatellite measurement signals. The high-gain Ka directional antenna is a 0.6m-diameter Cassegrain antenna with a gain better than 36.8dBi (±0.2°), receiving left-hand circular polarization and transmitting right-hand circular polarization; the low-gain Ka wide-beam antenna is a waveguide antenna, including a receiving antenna and a transmitting antenna, with a gain better than -6dBi (±60°), receiving right-hand circular polarization and transmitting left-hand circular polarization. The combination of the high-gain Ka directional antenna and the low-gain Ka wide-beam antenna takes into account both improving the intersatellite measurement distance and reducing the difficulty of intersatellite beam alignment; the master satellite ranging payload and the slave satellite ranging payload measure the intersatellite distance and time difference.

[0060] The main satellite platform provides power, second pulse signals, time broadcast and control instructions for the main satellite ranging payload, receives the inter-satellite measurement results and analog telemetry of the main satellite ranging payload, provides attitude adjustment and control for inter-satellite measurement, and transmits the measurement results to the ground.

[0061] The slave satellite platform provides power and control instructions for the slave satellite ranging payload, receives the inter-satellite measurement results and analog telemetry of the slave satellite ranging payload, provides attitude adjustment and control for inter-satellite measurement, and transmits the measurement results to the ground.

[0062] The primary and secondary satellites fly in a large elliptical frozen orbit around the moon, with the inter-satellite distance oscillating in the range of 50km to 700km.

[0063] The intersatellite measurement signal is a Ka-band radio frequency signal modulated with a pseudo code signal and an intersatellite measurement frame. The modulation mode is PCM-CDMA-BPSK, and the pseudo code rate is 10.23Mcps. The intersatellite measurement frame information code stream and the pseudo code sequence are XORed to generate a spread spectrum code sequence, which is BPSK modulated. The pseudo code signal is used to measure the time difference between the local timing signal and the received timing signal of the other party; the intersatellite measurement frame contains the time difference measurement result of the local satellite and the measurement timestamp. The master satellite and the slave satellite exchange the measurement results through the intersatellite measurement frame, so as to complete the settlement of the intersatellite distance and time difference on the local satellite.

[0064] The master satellite and the slave satellite obtain the pseudo-range measurement results of their own satellites through pseudo-code correlation operations, and then obtain the pseudo-range measurement results of each other from the inter-satellite measurement frame, and complete the calculation of the inter-satellite distance and time difference on the own satellite.

[0065] Specifically, the Ka channel module includes a transmitting channel and a receiving channel, and supports simultaneous transmission and reception. The transmitting channel up-converts, filters, and amplifies the center signal output by the digital baseband module and sends it to the antenna. The transmission power is 0.5W. The receiving channel amplifies, filters, and down-converts the RF signal from the antenna into an intermediate frequency signal, and outputs it to the digital baseband module. Both up-conversion and down-conversion adopt a single frequency conversion scheme.

[0066] The digital baseband module implements baseband signal processing and ranging algorithms: modulates the spread spectrum code sequence of inter-satellite measurement, digitally up-converts to generate an intermediate frequency signal, and outputs it to the Ka channel module; receives the intermediate frequency signal of the Ka channel module, performs pseudo code despreading, pseudo code synchronization, carrier synchronization and frame synchronization after digital down-conversion, uses pseudo code correlation operations to obtain the local satellite time difference measurement value required for the two-way time comparison method, analyzes the inter-satellite measurement frame to obtain the time measurement value of the other satellite; and calculates the inter-satellite distance and time difference;

[0067] The intermediate frequency transceiver circuit of the digital baseband module uses an integrated transceiver chip to realize the conversion of baseband data and intermediate frequency signals, meeting the requirements of miniaturization, low power consumption and flexibility; the digital signal processing circuit adopts FPGA chip to complete baseband data processing, and configures anti-fuse to refresh FPGA chip and watchdog reset circuit to improve the product's single-particle resistance; the clock generation circuit cascades the chip-level atomic clock and the tamed constant temperature crystal oscillator to provide reference clock and reference frequency for the digital baseband module and Ka channel module.

[0068] Furthermore, the master satellite adopts a high-gain Ka directional antenna to increase the distance of inter-satellite measurement. During inter-satellite measurement, the master satellite needs to adjust its attitude to align the antenna beam with the slave satellite, and the master satellite platform needs to have high attitude pointing accuracy and attitude stability. The slave satellite adopts a low-gain Ka wide-beam antenna to reduce the difficulty of inter-satellite pointing. During inter-satellite measurement, the slave satellite points the low-gain Ka wide-beam antenna in the direction or opposite direction of its speed according to its relative position relationship with the master satellite, and the slave satellite platform does not need high attitude pointing accuracy and attitude stability.

[0069] If the intersatellite measurement signal cannot be locked, the main satellite platform adjusts the satellite attitude and uses spiral scanning to adjust the beam pointing of the high-gain Ka directional antenna.

[0070] The master satellite is the initiator of intersatellite measurement, and the signal sending time of the slave satellite is synchronized with the master satellite; the master satellite platform sends a second pulse signal to the ranging payload. After the master satellite ranging payload receives the second pulse signal and determines it is valid, it starts to send intersatellite measurement signals at the falling edge of the second pulse. After the slave satellite ranging payload receives the signal and successfully demodulates it, it starts to send intersatellite measurement signals. After the master satellite ranging payload receives the signal from the slave satellite and successfully demodulates it, both parties start to measure using the two-way time comparison method. The slave satellite ranging payload corrects the sending time of the slave satellite signal according to the measurement results, and sends the time synchronization to the master satellite.

[0071] The present invention also provides a method for measuring the inter-satellite relationship of a microsatellite in a lunar orbit formation navigation. Figure 2 As shown, the method includes:

[0072] Step 1: The ground selects the intersatellite measurement arc and injects instructions to the satellite. Based on the orbit prediction, the ground calculates the arc where the distance between the master satellite and the slave satellite is less than 400km; the ground injects the satellite's orbital data and intersatellite measurement instructions to the master satellite and the slave satellite, including the satellite attitude adjustment time, ranging payload power on and off time, intersatellite measurement time, etc.

[0073] Step 2: The master and slave satellites adjust their attitudes. According to the orbital data recorded on the ground, the master satellite platform adjusts its attitude and points the high-gain Ka directional antenna toward the slave satellite; according to the positional relationship between the master and slave satellites, the slave satellite platform adjusts its attitude and points the low-gain Ka wide-beam antenna in the direction or opposite direction of its velocity.

[0074] Step 3: The ranging payloads of the master and slave satellites are powered on for 20 minutes. The satellite platform sends a power-on command to the ranging payload according to the ground-based command. This step is to wait for the output signal of the disciplined constant temperature crystal oscillator in the channel module to stabilize.

[0075] Step 4: The master and slave satellites establish an intersatellite link and the intersatellite measurement signal is locked. The master satellite platform sends a time broadcast and a pulse-per-second signal to the ranging payload. The master satellite ranging payload starts to send a timed intersatellite measurement signal to the slave satellite at the falling edge of the pulse-per-second. If the slave satellite cannot lock the master satellite signal, the master satellite platform adjusts the satellite attitude and uses a spiral scanning method to adjust the beam pointing of the high-gain Ka directional antenna.

[0076] After the slave satellite receives the master satellite signal and successfully demodulates it, it sends a timed inter-satellite measurement signal to the master satellite; the master satellite ranging payload receives the slave satellite signal and successfully demodulates it.

[0077] Step 5: The slave satellite sends synchronization signals to the master satellite. The master and slave satellites start to measure using the two-way time comparison method, filling the local satellite pseudo-range measurement results and measurement timestamps in the inter-satellite measurement frame; the slave satellite ranging payload parses the master satellite timestamp in the inter-satellite measurement frame and regards this moment as the starting time of the whole second point of the transmission signal of the slave satellite ranging payload.

[0078] Step 6: Obtain inter-satellite measurement results. The ranging payloads of the master and slave satellites respectively calculate the inter-satellite distance and time difference, and upload the measurement results and measurement timestamp to the local satellite platform; the satellite platform transmits the measurement results to the ground.

[0079] Step 7: The master satellite and the slave satellite restore the attitude towards the sun. After the intersatellite measurement is completed, the master satellite and the slave satellite turn off the ranging payload and adjust their attitude to the normal flight attitude towards the sun.

[0080] Next, the present invention will be described in more detail.

[0081] The present invention provides a lunar orbit formation navigation microsatellite intersatellite measurement system and method, which can establish an intersatellite measurement link within the range of 50km to 500km between satellites, and use a two-way time comparison method to achieve ranging accuracy better than meter level and nanosecond level time synchronization. The first two satellites do not need precise time synchronization or signal coherence before measurement, and both satellites can autonomously calculate the intersatellite distance.

[0082] A Ka inter-satellite link is established between the navigation master satellite and the slave satellite, and the inter-satellite distance and time difference are obtained by a two-way time comparison method based on a spread spectrum system; the master satellite and the slave satellite formation operate in a large elliptical frozen orbit around the moon, and the inter-satellite distance oscillates and changes; the master satellite includes a high-gain Ka directional antenna, a ranging payload and a satellite platform, and the slave satellite includes a low-gain Ka wide-beam antenna, a ranging payload and a satellite platform; the high-gain Ka directional antenna and the low-gain Ka wide-beam antenna complete the transmission and reception of inter-satellite measurement signals, and the ranging payloads of the master satellite and the slave satellite use a two-way time comparison method to measure the inter-satellite distance and time difference, the master satellite platform provides power, second pulse signals, time broadcasting and control instructions for the ranging payload, receives the inter-satellite measurement results and analog telemetry of the ranging payload, provides attitude adjustment and control for the inter-satellite measurement, and transmits the measurement results to the ground, the slave satellite platform provides power and control instructions for the ranging payload, receives the inter-satellite measurement results and analog telemetry of the ranging payload, provides attitude adjustment and control for the inter-satellite measurement, and transmits the measurement results to the ground.

[0083] The combination of high-gain Ka directional antenna and low-gain Ka wide-beam antenna takes into account both improving the inter-satellite measurement distance and reducing the difficulty of inter-satellite beam alignment.

[0084] The master satellite ranging payload and the slave satellite ranging payload have the same hardware design except that the transmitting and receiving frequencies are interchanged, including the Ka channel module and the digital baseband module.

[0085] The Ka channel module includes a transmitting channel and a receiving channel, supports simultaneous transmission and reception, up-converts, filters, amplifies the center signal output by the digital baseband module, and sends it to the Ka antenna, receives the RF signal from the Ka antenna, amplifies, filters, and down-converts it into an intermediate frequency signal, and outputs it to the digital baseband module; the up-conversion and down-conversion both adopt a single frequency conversion scheme.

[0086] The digital baseband module implements baseband signal processing and ranging algorithms: modulates the spread spectrum code sequence of inter-satellite measurement, digitally up-converts to generate an intermediate frequency signal, and outputs it to the Ka channel module; receives the intermediate frequency signal of the Ka channel module, performs pseudo code despreading, pseudo code synchronization, carrier synchronization and frame synchronization after digital down-conversion, uses pseudo code correlation operations to obtain the local satellite time difference measurement value required for the two-way time comparison method, and parses the inter-satellite measurement frame to obtain the time measurement value of the other satellite; calculates the inter-satellite distance and time difference;

[0087] The digital baseband module includes an intermediate frequency transceiver circuit, a digital signal processing circuit and a clock generation circuit. The intermediate frequency transceiver circuit uses an integrated transceiver chip to realize the conversion of baseband data and intermediate frequency signals, meeting the requirements of miniaturization, low power consumption and flexibility; the digital signal processing circuit uses an FPGA chip to complete baseband data processing, and is configured with an anti-fuse to refresh the FPGA chip and a watchdog reset circuit to improve the product's single-particle resistance; the clock generation circuit cascades a chip-level atomic clock and a tamed constant temperature crystal oscillator to provide a reference clock and reference frequency for the digital baseband module and the Ka channel module;

[0088] The difference between the master satellite and the slave satellite is that the master satellite adopts a high-gain Ka directional antenna to increase the distance of inter-satellite measurement. During inter-satellite measurement, the master satellite needs to adjust its attitude to align the antenna beam with the slave satellite. If the inter-satellite measurement signal cannot be locked, the master satellite platform adjusts the satellite attitude and uses a spiral scanning method to adjust the beam pointing of the high-gain Ka directional antenna. The master satellite platform needs to have high attitude pointing accuracy and attitude stability; the slave satellite adopts a low-gain Ka wide-beam antenna to reduce the difficulty of inter-satellite pointing. During inter-satellite measurement, the slave satellite points the low-gain Ka wide-beam antenna in the direction or opposite direction of its speed according to its relative position relationship with the master satellite. The slave satellite platform does not need high attitude pointing accuracy and attitude stability;

[0089] The difference between the master satellite and the slave satellite also lies in that the master satellite is the initiator of intersatellite measurement, and the signal sending time of the slave satellite is synchronized with the master satellite; the master satellite platform sends a second pulse signal to the ranging payload. After the master satellite ranging payload receives the second pulse signal and determines it to be valid, it starts sending intersatellite measurement signals at the falling edge of the second pulse. After the slave satellite ranging payload receives the signal and successfully demodulates it, it starts sending intersatellite measurement signals. After the master satellite ranging payload receives the signal from the slave satellite and successfully demodulates it, the two parties start to measure using the two-way time comparison method. The slave satellite ranging payload corrects the sending time of the slave satellite signal according to the measurement results, and sends it to the master satellite at the same time.

[0090] The two-way time comparison method is that both the master satellite and the slave satellite send timing signals and receive timing signals from each other, measure the time difference between the local timing signal and the received timing signal of the other party, and the two satellites exchange the measured time difference through the inter-satellite link to solve the inter-satellite distance and time difference; the distance measurement principle of the two-way comparison method does not belong to the scope of the invention of the present invention;

[0091] The inter-satellite measurement signal is a Ka-band radio frequency signal modulated with a pseudo code signal and an inter-satellite measurement frame. The pseudo code signal is used to measure the time difference between the local timing signal and the received timing signal of the other party. The inter-satellite measurement frame contains the time difference measurement result of the local satellite and the measurement timestamp. The master satellite and the slave satellite exchange measurement results through the inter-satellite measurement frame, thereby completing the settlement of the inter-satellite distance and time difference on the local satellite.

[0092] The embodiment of the present invention provides a lunar orbit formation navigation microsatellite inter-satellite measurement system and method, which does not require precise time synchronization between two satellites, and the measurement results can be obtained directly on the satellite without ground solution, thus saving ground resources; simplifying the satellite platform and antenna design of the slave satellite, reducing the weight and cost of the satellite.

[0093] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0094] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A lunar orbit formation navigation microsatellite intersatellite measurement system, characterized in that: include: A Ka inter-satellite link is established between the master satellite and the slave satellite; The master satellite and the slave satellite both send timing inter-satellite measurement signals and receive timing inter-satellite measurement signals from each other, measure the time difference between the local timing signal and the received timing signal of the other party to obtain the local satellite pseudo-range, and the two satellites exchange pseudo-ranges through an inter-satellite link, that is, solve the inter-satellite distance and time difference.

2. The lunar orbit formation navigation microsatellite intersatellite measurement system according to claim 1, characterized in that: The master satellite includes: a high-gain Ka directional antenna, a master satellite ranging payload and a master satellite platform; the slave satellite includes: a low-gain Ka wide-beam antenna, a slave satellite ranging payload and a slave satellite platform; The high-gain Ka directional antenna and the low-gain Ka wide-beam antenna complete the transmission and reception of intersatellite measurement signals; The master satellite ranging payload and the slave satellite ranging payload measure the inter-satellite distance and time difference; The master satellite platform provides power, pulse-per-second signals, time broadcast and control instructions for the master ranging payload, receives intersatellite measurement results and analog telemetry of the master ranging payload, provides attitude adjustment and control for intersatellite measurement, and transmits the measurement results to the ground; The slave satellite platform provides power and control instructions for the slave ranging payload, receives inter-satellite measurement results and analog telemetry of the slave ranging payload, provides attitude adjustment and control for inter-satellite measurement, and transmits the measurement results to the ground.

3. The lunar orbit formation navigation microsatellite intersatellite measurement system according to claim 2, characterized in that: The master satellite adopts a high-gain Ka directional antenna. During inter-satellite measurement, the master satellite needs to adjust its attitude to align the antenna beam with the slave satellite. The slave satellite adopts a low-gain Ka wide-beam antenna. During inter-satellite measurement, the slave satellite points the low-gain Ka wide-beam antenna in the direction of its velocity or in the opposite direction according to its relative position relationship with the master satellite.

4. The lunar orbit formation navigation microsatellite intersatellite measurement system according to claim 3, characterized in that: If the intersatellite measurement signal cannot be locked, the master satellite platform adjusts the satellite attitude and uses a spiral scanning method to adjust the beam pointing of the high-gain Ka directional antenna.

5. The lunar orbit formation navigation microsatellite intersatellite measurement system according to claim 2, characterized in that: The master satellite is the initiator of intersatellite measurement, and the slave satellite is synchronized with the master satellite at the time of signal transmission; The master satellite platform sends a pulse-per-second signal to the ranging payload. After the master satellite ranging payload receives the pulse-per-second signal and determines it is valid, it starts sending intersatellite measurement signals at the falling edge of the pulse-per-second signal. After the slave satellite ranging payload receives the signal and successfully demodulates it, it starts sending intersatellite measurement signals. After the master satellite ranging payload receives the slave satellite signal and successfully demodulates it, both parties start measuring using the two-way time comparison method. The slave satellite ranging payload corrects the sending time of the slave satellite signal based on the measurement results and sends it to the master satellite for time synchronization.

6. The lunar orbit formation navigation microsatellite intersatellite measurement system according to claim 2, characterized in that: The master satellite ranging payload and the slave satellite ranging payload both include: a Ka channel module and a digital baseband module; The Ka channel module includes: a transmitting channel and a receiving channel, which support simultaneous transmission and reception. The transmitting channel up-converts, filters, and amplifies the central signal output by the digital baseband module and sends it to the antenna. The receiving channel amplifies, filters, and down-converts the radio frequency signal from the antenna into an intermediate frequency signal and outputs it to the digital baseband module. Both up-conversion and down-conversion adopt a single frequency conversion scheme. The digital baseband module implements baseband signal processing and ranging algorithms, modulates the spread spectrum code sequence of inter-satellite measurement, digitally up-converts the frequency to generate an intermediate frequency signal, and outputs the signal to the Ka channel module; receives the intermediate frequency signal of the Ka channel module, performs pseudo code despreading, pseudo code synchronization, carrier synchronization and frame synchronization after digital down-conversion, obtains the local satellite time difference measurement value required by the two-way time comparison method by using pseudo code correlation operation, analyzes the inter-satellite measurement frame to obtain the time measurement value of the other satellite; and calculates the inter-satellite distance and time difference.

7. The lunar orbit formation navigation microsatellite intersatellite measurement system according to claim 6, characterized in that: The digital baseband module includes: an intermediate frequency transceiver circuit, a digital signal processing circuit and a clock generation circuit; The intermediate frequency transceiver circuit uses an integrated transceiver chip to realize the conversion between baseband data and intermediate frequency signals, meeting the requirements of miniaturization, low power consumption and flexibility; The digital signal processing circuit uses an FPGA chip to complete baseband data processing, and is configured with an anti-fuse to refresh the FPGA chip and a watchdog reset circuit to improve the product's single-particle resistance; The clock generation circuit cascades a chip-level atomic clock and a tamed constant temperature crystal oscillator to provide a reference clock and a reference frequency for a digital baseband module and a Ka channel module.

8. The lunar orbit formation navigation microsatellite intersatellite measurement system according to claim 1, characterized in that: The inter-satellite measurement signal is a Ka-band radio frequency signal of a modulated pseudo code signal and an inter-satellite measurement frame; The pseudo code signal is used to measure the time difference between the local timing signal and the received timing signal of the other party; The inter-satellite measurement frame includes the time difference measurement result of the local satellite and the measurement timestamp. The master satellite and the slave satellite exchange the measurement results through the inter-satellite measurement frame, thereby completing the settlement of the inter-satellite distance and time difference on the local satellite.

9. A method for inter-satellite measurement of a lunar orbit formation navigation microsatellite, based on the inter-satellite measurement system of a lunar orbit formation navigation microsatellite according to any one of claims 1 to 8, characterized in that: include: Step 1: The ground selects the intersatellite measurement arc according to the orbit prediction and sends instructions to the satellite; Step 2: The master satellite platform and the slave satellite platform adjust their attitudes; Step 3: The ranging payloads of the master and slave satellites are turned on for a set threshold time; Step 4: The master satellite and the slave satellite establish an inter-satellite link, and the inter-satellite measurement signal is locked; Step 5: The slave satellite sends synchronization signals to the master satellite; Step 6: Obtain intersatellite measurement results; Step 7: After the intersatellite measurement is completed, the master satellite and the slave satellite turn off the master satellite ranging payload and the slave satellite ranging payload, and the master satellite and the slave satellite adjust their attitude to the normal flight attitude towards the sun.

10. The method for inter-satellite measurement of a microsatellite in lunar orbit formation navigation according to claim 9, characterized in that: The step 4 comprises: The master satellite platform sends time broadcast and second pulse signals to the ranging payload, and the master satellite ranging payload starts to send timed inter-satellite measurement signals to the slave satellite at the falling edge of the second pulse; If the slave satellite cannot lock onto the master satellite signal, the master satellite platform adjusts the satellite attitude and uses spiral scanning to adjust the beam pointing of the high-gain Ka directional antenna; After the slave satellite receives the master satellite signal and successfully demodulates it, it sends a timed inter-satellite measurement signal to the master satellite; the master satellite ranging payload receives the slave satellite signal and successfully demodulates it.

Images